I'm not sure you are interpreting that correctly because there is no way Rick recommends your jib leads to be back that far. A quick and dirty start is to start at a point in the middle of the luff of your jib, draw a line through the clew, and then to the trampoline. You will probably find that you need to be a little more forward than this.

The entire idea behind the sheeting angle is to make the shape of the jib consistent from top to bottom as it us presented to the wind. With a set of tell-tales approximately 1/3 from the top and 1/3 up from the bottom, if you steer your boat up into a luff, both sets of tell-tales should break at about the same time. If the top breaks before the bottom, the bottom is too flat and you need to move your jib lead further forward on the deck and vice versa. That is roughly the ideal power point for the jib. In higher wind, you may want to move the lead further back to let the top twist open a little and so forth.